With the rapid development of the communication technology, the network of domestic wireless communication operators and the number of their users have greatly increased. With the aggravation of the market competition, the quality of the mobile communication network, which has been a powerful guarantee for further developing users and reducing the rate of its users from cutting off its network, has become one of the key factors to determine the competitions among the operators? Factors affecting the quality of the mobile communication network can be mainly divided into three categories: the rationality of network project, the performance quality of network equipments and the construction quality on the spot. Among these three factors, the antenna working parameter data at the base station is the most basic element, and the measurement for the working parameters is the most basic work among its production work for the communication base station's antenna construction, maintenance and optimization. Only based on a complete and reliable working parameter, can the network project and optimization guarantee the quality of the communication network efficient and accurate.
The antenna working parameter data mainly includes azimuth, pitch angle, roll angle, hanging height and its location, etc. Azimuth usually has zero degree angle in the north direction and 180 degree angle in the south direction, which clockwise increases its angle. The antenna azimuth depends on its location and an accurate azimuth can ensure the actual coverage of a base station is accorded with the expected one so as to guarantee its operation quality of the network. The antenna azimuth can be properly adjusted to optimize the existing communication network on the basis of its concrete conditions or network communication traffic. The pitch angle includes depression angle (i.e. declination angle) and elevation angle (i.e. upward elevation angle). The antenna's electromagnetic wave will have a certain coverage field, and its boundary will overlap the other antenna's wave field. Hence, selecting an appropriate pitch angle can make the overlap coverage be reduced to a minimum level so that the signal interference between two adjacent areas can be minimized. If the pitch angle is too small, which can lead to signal overlay and overlap between two neighboring regions, switch confusion between two adjacent coverage areas will occur and signal interference in the system will be serious. If the pitch angle is too big, it will cause signal blind area or weakness zone within the coverage field, and at the same time, it will cause severe distortion of antenna's direction image along with severe signal interference in the system. The roll angle is one of the necessary parameters to describe the space attitude of an object. The traditional antenna working parameters hasn't got roll angles, since the previous testing means was limited and the importance of the rob angle was neglected.
While installing antenna on the base station, try to ensure that the longitudinal section, which goes through the antenna center, will be always perpendicular to the ground. Thus, the antenna roll angle is zero degree. But in fact, due to the restriction of the installation level and later the external force, a considerable proportion of the antenna roll angle has of a large deviation from zero degree. Large non-zero roll angle will cause the electromagnetic wave, which needs to cover a certain direction, to deviate significantly from the expected field, causing the relevant planning leads to an inaccurate optimization. For example, when the antenna slopes, namely, the angle inclination and its longitudinal section are not on the same plane, adding in the roll angle, the antenna space attitude can only be described and the electromagnetic wave specific coverage can be accurately calculated. Antenna attitude measurement is to accurately measure the working parameters of antenna attitude and provide a reliable basis for the network construction.
In the traditional antenna attitude measurement, the workers take use of multiple tools for manual measurement. The antenna azimuth angle is determined artificially through the use of a compass. Since the magnetic lines have got poor consistency, the compass is vulnerably restricted to natural conditions, unable to provide consistent directional measurement. For example, at some point on earth, its declination may be a few degrees to 20 degrees, and the geomagnetic index can be affected by magnetic storms, the minerals on the earth are distributed unevenly. All these factors may cause changes of the north magnetic pole. Generally on the earth, the direction of magnetic lines can be guaranteed consistent only within a few kilometers, but with so many electrical equipments, buildings automobiles and steels in the city, the magnetic field in a small range will change and will be more difficult to compensate. The antenna itself on a base station will send electromagnetic wave of tens of watts. And the base station itself is composed of a large number of steel towers welded together with high density. Accurate compensation at proximal magnetic field can't be obtained with regularity, etc. All these are the factors that initiate the azimuth cannot be precisely measured. The measurement of antenna pitch angle is determined by the working staff who will check the scales marked on the antenna tower. Since the scales have got low precision and the engineers possess different working skills and different measuring methods, it will make the measurement results produce large errors, which will be unable to achieve the requirements for accurate designs.